25.3.4.1 Flags for Argp Options

The following flags may be or’d together in the flags field of a struct argp_option. These flags control various aspects of how that option is parsed or displayed in help messages:

OPTION_ARG_OPTIONAL

The argument associated with this option is optional.

OPTION_HIDDEN

This option isn’t displayed in any help messages.

OPTION_ALIAS

This option is an alias for the closest previous non-alias option. This means that it will be displayed in the same help entry, and will inherit fields other than name and key from the option being aliased.

OPTION_DOC

This option isn’t actually an option and should be ignored by the actual option parser. It is an arbitrary section of documentation that should be displayed in much the same manner as the options. This is known as a documentation option.

If this flag is set, then the option name field is displayed unmodified (e.g., no ‘--’ prefix is added) at the left-margin where a short option would normally be displayed, and this documentation string is left in its usual place. For purposes of sorting, any leading whitespace and punctuation is ignored, unless the first non-whitespace character is ‘-’. This entry is displayed after all options, after OPTION_DOC entries with a leading ‘-’, in the same group.

OPTION_NO_USAGE

This option shouldn’t be included in ‘long’ usage messages, but should still be included in other help messages. This is intended for options that are completely documented in an argp’s args_doc field. See Argp Parsers. Including this option in the generic usage list would be redundant, and should be avoided.

For instance, if args_doc is "FOO BAR\n-x BLAH", and the ‘-x’ option’s purpose is to distinguish these two cases, ‘-x’ should probably be marked OPTION_NO_USAGE.